1. Field of the Invention
This invention relates generally to a method of continuous production of disks that have a thin film coat and more particularly to a method of exchanging a disk tray after a film buildup has occurred without interrupting production of the couture.
2. Description of the Prior Art
Media disks are coated with a thin film by coaters, well known in the art. Such coaters include the Unaxis Big Sprinter Coater manufactured by Unaxis, located at Balzers, Liechtenstein. The thin film coaters have an automated disk loader mechanism. This disk loader mechanism has a double ended transfer arm that transfers a single disk with metal ID and OD masks from the vacuum coater to a position where the thin film coated disk can be picked from the ID and OD masks and replaced with an uncoated disk. The removal of the thin film coated disk from this position and replacement of it with a not thin film coated disk can be done by human hand but is typically done by external automated disk handling equipment that is not part of the disk coater. On each thin film machine cycle the thin film coated disk is replaced with an uncoated disk. The ID and OD metallic masks are not replaced until thin film coatings have built up to the extent that they begin to flake from the metallic masks or to the extent that ID mask has increased in size or the OD mask opening has decreased in size as to not allow thin films to coat an adequate surface area of the disk. At this point, the ID and OD masks with thin film coating build up are replaced with masks that have had the thin film coatings removed. This mask exchange is typically done at what is referred to as an intermediate disk loader position. The disk loader transfer arm of the coater stops at 90 degrees between its load and unload position and ID and OD masking can be replaced. The foregoing description was for larger disks, typically 120 mm in diameter. The external handling that removes a coated disk and replaces it with an uncoated disk is not part of the thin film coating machine. The mask exchange is part of the thin film machine. The 120 mm disks are typically coated and masked on only one side.
It is no longer necessary or desirable to always have disks of 120 mm in diameter. New technology has become available which is able to utilize a disk of 32 mm. Since these are substantially smaller, multiples of these small disks are coated at once. Six small disks may be placed in a disk tray. The disk tray is used to hold the smaller disks and mask the outer diameter of the smaller disk. However, because six smaller disks are coated at the same time, an additional piece of handling equipment is necessary to load and unload the 6 disks contained within a disk tray and to place the disk tray to the position of the thin film coater disk loader mechanism where a single 120 mm substrate was formerly loaded. The ID and OD masks used for the 120 mm substrate are not used when coating the 32 mm substrates. One suitable piece of handling equipment is a Steag Hama Tech disk/tray handler manufactured by Steag Hama Tech of Sternenfels, Germany. The Steag disk/tray handler has been utilized to provide a loaded disk tray to the disk loading position of the coater. The disk trays become coated, after time, the same way that the masks did for the larger disks. Therefore, the disk trays have been exchanged at the same intermediate disk loading position as the exchange took place for the masks for the larger disks. Such an exchange, while only necessary every four to eight hours, does cause substantial disruption to the continuous, automated production of the coated disks.
In one embodiment, the invention is a method of exchanging a thin film coated tray for a clean tray for use with a thin film coater and a multiple position disk/tray handler. The disk/tray handler has a disk load position, disk transfer position, disk unload position and an intermediate position. The method includes loading a first tray, containing disks to be coated, onto the disk/tray handler at the disk load position. Then, the disk/tray handler is moved to the disk transfer position where the first tray is loaded into the thin film coater and coating the disks in the first tray takes place. Then, the first tray is returned from the coater to the disk load position. The disk/tray handler is then moved to the disk unload position and the disks that have been coated are removed. The disk/tray handler is then moved through an intermediate position to the disk load position. The previous steps are repeated until prior to the first tray needing to be replaced. The first tray, containing disks to be coated is loaded, onto the disk/tray handler at the disk load position. Then, the disk/tray handler is moved to the disk transfer position where the first tray is loaded into the thin film coater and coating the disks in the first tray takes place. Then, the first tray is returned from the coater to the disk load position. The disk/tray handler is then moved to the disk unload position and the disks that have been coated are removed. The first tray is then moved to the intermediate position. The first tray is removed from the intermediate position and a second, clean tray is placed in the intermediate position to replace the first tray.
In another embodiment, the invention is a method of exchanging a thin film coated tray for a clean tray. The method includes loading a first tray, containing disks to be coated, onto a disk/tray handler at a disk load position. The disk/tray handler is then moved to a disk transfer position. At the disk transfer position, the first tray is loaded into a film coater and the disks are coated in the first tray. The first tray is returned from the coater to the disk/tray handler. The disks that have been coated are unloaded at a disk unload position. The disk/tray handler is moved to move the first tray to an intermediate position. The first tray is removed from the disk/tray handler at the intermediate position and a second, clean tray, is placed in the intermediate position to replace the first tray, whereby production of the coater is continuous, without interruption of exchanging trays.